The present invention relates to golf clubs and, in particular, to a wood type golf club head having an improved ball striking face configuration.
Traditionally wood type and metalwood type golf club heads have been provided with a bulge radius on the ball striking face used to offset the gear effect spin experienced when a ball is hit off of the center of percussion, that is toward the heel or toe. The bulge radius is the circular radius of the ball striking face in a horizontal plane with the club head positioned such as it would be positioned at address behind a golf ball prior to the execution of a golf stroke.
In a traditional golf club having a symmetrical club face configuration, the center of the radius of curvature of the bulge of the club face lies on a line perpendicular to the face angle of the club head and intersecting the geometrical center of the club face striking surface. The apex of the bulge radius is located at the point where this perpendicular line intersects the ball striking face. The face angle of the club face is defined by a horizontal line that forms a predetermined angle with a line extending from the geometric center of the club face to the target where the ball is intended to be hit. A square club face angle is perpendicular to the target line while a closed face angle is perpendicular to a line pointed left of target and an open face angle is perpendicular to a line pointed right of target.
The bulge radius controls the ball launch direction, but has no significant influence on the magnitude of the gear effect spin. Its purpose is to start a golf ball further to the right on toe shots and further to the left on heel shots, which creates a correction or compensation factor when the ball is struck off of the center of the club head, which, in turn, causes unwanted side spins resulting in hooking or slicing from the intended target.
When a golf ball is struck on a ball striking face, spin will be imparted if the golf ball is struck off center due to the well known gear effect phenomenon which is a function of the center of gravity location of the club head relative to where the golf ball is struck. For example, a golf ball struck toward the heel will have side spin that causes the ball to spin to the right of the intended target line. Similarly, a golf ball hit toward the toe has side spin which induces the ball to spin to the left of the target line.
The bulge radius of a golf club head does not effect the side spin imparted to a ball, however, it does effect the line of flight direction as the ball initially leaves the club face. For example, a ball hit toward the heel of the club head with too small a bulge radius will be launched too far left to the extent that the side spin is insufficient to enable a ball to recover its overall direction to the intended target line. Similarly, a ball hit on the toe will be launched too far right and the side spin will not be sufficient to bring the ball back to the target line.
Ideally, depending upon the gear effect spin a club produces as a function of the center of gravity location in the club head, the bulge radius may be adjusted to offset the ball flight curvature created by the spin to bring the ball back to the intended target line whether it is hit off center toward the heel or off center toward the toe.
Prior art golf clubs which are adjusted to provide a directional tendency either close or open the club face angle while leaving the club face configuration symmetrical. For example, a golf club with a left directional tendency would have a club face closed, for example, by two degrees, to overcome the right directional tendency of golfers who slice. Similarly, a golfer who draws a golf ball may use a club head with a one degree open face to hit straighter shots.
There have been some efforts made in the prior patented art to adjust the configuration of the ball striking face to affect the flight of the ball being struck by the club head. For example, U.S. Pat. No. 5,098,103 to MacKeil shows a golf club head having a fixed compensating loft where the face loft angle varies from the toe to the heel and is more lofted toward the heel than the toe. The purpose is to effect the ball trajectory when the ball is struck off of the center of gravity on the club face, thereby maintaining a more nearly constant loft angle.
U.S. Pat. No. 4,771,961 to Masghati et al. shows a golf club with a bulge radius where the weight is distributed on opposite sides of a non-vertical axis extending through the center of gravity such that wood type golf club heads have bulge and roll which curve about this axis and at an axis perpendicular thereto. Thus, the striking face has a convex curvature about a first axis which extends parallel to a second axis which extends through the center of gravity of the club head. These first and second axes lie in a plane which extends through the center of the striking face and which intersect the center line of the shaft above the club head.
U.S. Pat. No. 4,367,878 to Schmidt is directed to a golf club head having a bulge curvature defined by the intersection of generally horizontal planes normal to the ball striking face. These intersections defining curved lines which are generally parabolic when viewed from a position above the club head and spaced rearwardly of a line normal to the bottom surface such that the front face is tilted rearwardly.
The present invention relates to a golf club head with a directional tendency having an asymmetrical bulge or having a bulge radius apex displaced from the face center to control golf ball launch direction from the club face for golfers that tend to slice or hook a golf ball. The club head combines an asymmetrical or displaced bulge configuration with an appropriate gear effect to provide a launch direction minimizing hook and slicing spin. The structure of the club head will allow a large majority of golfers that tend to slice to hit straighter shots. Similarly, a golf club made in accordance with the present invention with an asymmetrical ball striking face can be used to minimize the misdirection of hooked golf shots.
Therefore, golf clubs made in accordance with the present invention will have a directional tendency so a golfer with a tendency to slice will be able to use a golf club with a left directional tendency and a golfer who tends to hook the ball will be able to use a golf club with a right directional tendency. For example, by increasing the bulge radius on the toe and decreasing the radius on the heel, a golf club is created with a left directional tendency. Similarly, a left directional tendency can be created by moving the apex of the bulge radius toward the toe. In like manner, providing a large radius on the heel and a smaller radius on the toe, creates a golf club having a right directional tendency. This also can be achieved by moving the apex toward the heel. The bulge configuration of the ball striking face of the golf club head is determined through test and analysis. The local face angle at the apex can be calculated for any given bulge configuration and apex location to guide the test and analysis.
An object of the present invention is the provision of a golf club head having an asymmetric shape for the purpose of changing the directional tendency of the club head.
Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention.